Networked virtual environments allow users at remote locations to use a telecommunication link to coordinate work and social interaction. Teleconferencing systems and virtual environments that use 3D computer graphics displays and digital video recording systems allow remote users to interact with each other, to view virtual work objects such as text, engineering models, medical models, play environments and other forms of digital data, and to view each other's physical environment.
A number of teleconferencing technologies support collaborative virtual environments which allow interaction between individuals in local and remote sites. For example, video-teleconferencing systems use simple video screens and wide screen displays to allow interaction between individuals in local and remote sites. However, wide screen displays are disadvantageous because virtual 3D objects presented on the screen are not blended into the environment of the room of the users. In such an environment, local users cannot have a virtual object between them. This problem applies to representation of remote users as well. The location of the remote participants cannot be anywhere in the room or the space around the user, but is restricted to the screen.
Head-mounted displays (HMDs) have been widely used for 3D visualization tasks such as surgical planning, medical training, or engineering design. The main issues of the conventional eyepiece-based HMD technology include tradeoffs between resolution and field-of-view (FOV), and between compactness and eye clearance, the presence of large distortion for wide FOV designs, the conflict of accommodation and convergence, the occlusion contradiction between virtual and real objects, the challenge of highly precise registration, and often the brightness conflict with bright background illumination. The concept of head-mounted projective displays (HMPDs) is an emerging technology that can be thought to lie on the boundary of conventional HMDs, and projective displays such as the CAVE technology.
The basic HMPD concept of projection head-mounted display was first patented by Fisher Nov. 5, 1996, in U.S. Pat. No. 5,572,229. On Apr. 15, 1997, a U.S. Pat. No. 5,621,572 was also issued to Ferguson on the conceptual idea of a display, i.e. optical, system for head mounted display using retro-reflector and method of displaying an image.
Common to all teleconferencing systems is the use of lenses of various configurations and weights with distortions, lack of clarity and smearing of the televised images. Representative of lenses that might at first glance appear to be useful in the teleconferencing systems are also shown in:
U.S. Pat. No. 5,526,183 by Chen who teaches the use of a lens combining diffractive elements of both glass and plastics to reduce the weight and size of the lens which lens within a conventional helmet mounted display;
U.S. Pat. No. 5,173,272 by Aoki which discloses a four element high aperture lens with glass elements making it too heavy for helmet mounting;
U.S. Pat. No. 4,753,522 by Nishina et al which lens features all 4 plastic elements and is fully symmetrical which latter property is imposed by its restricted application—a copy machine lens; and,
U.S. Pat. No. 4,669,810 by Wood which shows a head-mounted display with many (more than 4) optical elements in the relay optics.
There is a need for a HMPD reality display that mitigates the above mentioned disadvantages and has the capability to provide a widened field of view (FOV), i.e., greater than 120 degrees. Lightweight and compactness are always of basic importance and/or highly desirable for head-mounted devices but of even greater importance is those that display a wider FOV with high resolution.